Many-Body Physics in Few-Channel Quantum Circuits

The electronic conduction channel constitutes the elementary building block of quantum conductors. A fascinating many-body quantum physics arises from the interactions between electrons transferred across individual quantum channels, and the circuit macroscopic quantum degrees of freedom, such as the charge in a metallic node. The quantum electrodynamics at work results in electrical and thermal properties markedly different from those of the constitutive quantum channels. Apprehending these quantum laws has direct implications for the quantum engineering in the future nanoelectronics. Most remarkably, such quantum circuits composed of a few distinct conduction channels also provide formidable test-beds for the strongly-correlated electron physics, including the quantum criticality that develops in the vicinity of quantum phase transitions, the correlated 1D (Luttinger liquid) physics and the Kondo-type physics.

Figure 1: The central metallic island (bright) constitutes a circuit node. It is electrically connected to large reservoirs (not shown) through several quantum conductors tuned by field effect using voltage biased gates (green and yellow). The adjacent gates (blue) allow for the individual characterization of the constitutive quantum conductors.

Figure 2: Development of a quantum phase transition across the symmetric quantum critical point. The sample is designed to exhibit the two-channel Kondo effect. The continuous lines (arrows pointing to low temperatures) display the renormalization flow of the conductances of two quantum (Kondo) channels as temperature is reduced.